|Publication number||US7852822 B2|
|Application number||US 11/021,310|
|Publication date||Dec 14, 2010|
|Priority date||Dec 22, 2004|
|Also published as||CA2591938A1, CN101120565A, EP1836820A1, US9356752, US20060133388, US20110058469, WO2006069319A1|
|Publication number||021310, 11021310, US 7852822 B2, US 7852822B2, US-B2-7852822, US7852822 B2, US7852822B2|
|Inventors||Michael Mao Wang, Bojan Vrcelj, Krishna Kiran Mukkavilli, Raghuraman Krishnamoorthi, Rajiv Vijayan|
|Original Assignee||Qualcomm Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (46), Non-Patent Citations (7), Referenced by (2), Classifications (10), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The embodiments relate generally to data communications, and more particularly to systems and methods for structuring network IDs into OFDM symbols utilized in a wireless communication system.
The introduction of wireless technology for personal communications has almost made the traditional telephone a thing of the past. As wireless technologies improve, the sheer numbers of parties desiring to communicate wirelessly keep increasing substantially. “Cell” phones have developed into multifunctional devices that not only function to relay voice communications, but data as well. Some devices have also incorporated interfaces to the Internet to allow users to browse the World Wide Web and even download/upload files. Thus, the devices have been transformed from a simple voice device to a “multimedia” device that enables users to receive/transmit not only sound, but also images/video as well. All of these additional types of media have tremendously increased the demand for communication networks that support these media services. The freedom to be ‘connected’ wherever a person or device happens to be located is extremely attractive and will continue to drive future increases in wireless network demand.
Thus, the ‘airwaves’ in which wireless signals are sent become increasingly crowded. Complex signals are employed to utilize signal frequencies to their fullest extent. However, due to the sheer numbers of communicating entities, it is often not enough to prevent interference of signals. Network identification (ID) is typically transmitted with data so that a receiving entity knows the origination of the data. When interferences occur, a receiving entity may not be able to properly interpret what network the signal originated from and may lose information. This drastically reduces the efficiency of a communication network, requiring multiple sends of the information before it can be properly received. In the worst case, the data may be totally lost if it cannot be resent. If a network has hundreds or even thousands of users, the probability of not being able to identify a network ID increases substantially. The demand for wireless communications is not decreasing. Therefore, it is reasonable to assume that signal interferences will continue to increase, degrading the usefulness of existing technology. A communication system that can avoid this type of data corruption will be able to provide increased reliability and efficiency to its users.
The following presents a simplified summary in order to provide a basic understanding of some aspects of the embodiments. This summary is not an extensive overview of the embodiments. It is not intended to identify key/critical elements of the embodiments or to delineate the scope of the embodiments. Its sole purpose is to present some concepts of the embodiments in a simplified form as a prelude to the more detailed description that is presented later.
The embodiments relate generally to data communications, and more particularly to systems and methods for structuring network IDs into OFDM symbols utilized in a wireless communication system. Multiple network IDs are encoded into symbols utilizing the network IDs as seeds to scramble respective pilots that are then transmitted utilizing the symbols. The pilots can be structured into a single OFDM symbol and/or multiple OFDM symbols. The single symbol structure for transmitting the network IDs is independent of the number of network ID bits and minimizes frequency offset and Doppler effects, providing a high spreading gain of network ID data that is highly resistant to interference from other network ID broadcasts. The multiple symbol structure, however, allows a much coarser timing accuracy to be employed at the expense of transmitting additional symbols. One embodiment is a method for facilitating data communications that utilizes at least one OFDM symbol structured with at least one pilot respective of a network ID for communicating the network ID between entities. Another embodiment is a system that facilitates data communications that includes a communication component that communicates at least one network ID between entities by utilizing at least one OFDM symbol that includes at least one pilot respective of the network ID.
Several embodiments employ a search function to find possible network ID candidates from a transmitted symbol and a selection function to find an optimum candidate from the network ID candidate list. When multiple network IDs are structured into received symbols, typically, a first network ID is determined and utilized to facilitate in determining a second network ID. By employing metrics, a score or value can be assigned to each possible ID and an optimum set of network IDs can be determined by maximizing the score of the set of IDs. Thus, the embodiments provide a robust, cost-effective means to substantially reduce network ID interferences and increase network ID data reception.
To the accomplishment of the foregoing and related ends, certain illustrative embodiments are described herein in connection with the following description and the annexed drawings. These embodiments are indicative, however, of but a few of the various ways in which its principles may be employed and is intended to include all such embodiments and their equivalents.
The embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It may be evident, however, that the embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the embodiments. As used in this application, the term “component” is intended to refer to an entity, either hardware, software, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to being, a processor, a process running on a processor, and/or a multiplexer and/or other signal facilitating devices and software.
In accordance with the embodiments and corresponding disclosure thereof, various aspects are described in connection with a subscriber station. A subscriber station can also be called a system, a subscriber unit, mobile station, mobile, remote station, access point, base station, remote terminal, access terminal, user terminal, user agent, or user equipment. A subscriber station may be a wireless telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem.
The embodiments provide systems and methods to facilitate communication of network IDs in wireless systems. Utilization of OFDM symbols provides a means to transmit and receive pilots that have been scrambled based upon a respective network ID. By decoding the scrambled pilots, the network IDs can be retrieved. In this manner, dedicated symbols can provide a robust mechanism for relaying network IDs, substantially reducing interference from other networks. Additionally, the embodiments allow for multiple network IDs to be communicated in a single symbol or in multiple symbols. A single symbol structure requires more fine timing accuracy, while the multiple symbol structure requires coarse timing accuracy, but at the cost of additional symbols. A typical embodiment of a multiple structure utilizes separate symbols for each network ID to be communicated.
Reception and decoding of the network IDs is generally obtained utilizing a two stage process that includes a search process (that can be implemented by a search component) for finding a list of possible network ID candidates and a selection process (that can be implemented by a selection component) for selecting an optimum candidate from the candidate network ID list. The embodiments provide multiple means for determining the network IDs dependent upon the method utilized to encode the network ID into the symbol(s). Thus, a single symbol that contains a two network ID structure of interleaved pilots utilizes a different method of decoding than a dual symbol structure that contains a separate symbol for each network. The selection process itself can be eliminated by only maintaining a top scored value that is determined by a search metric. This essentially reduces a possible network ID candidate list to only a single choice, negating the necessity of having a follow-on selection process.
Typically, mobile wireless units are not aware of what networks are available in a particular area. In order for these units to operate, they must acquire network IDs by intercepting them from wireless signals. Normally, there are wide area networks and local area networks in a reception area that each has its own IDs. These IDs act as keys to facilitate in decoding program material. In a high traffic area, however, it may be difficult for a mobile device to properly interpret network IDs due to interference by other networks in the area.
In some communication systems, for example, two layers of network IDs exist such as, for example, network ID type A and network ID type B. Typically, a wireless system needs to acquire network ID type A to decode type A program material and needs to acquire both network ID type A and network ID type B to decode type B programs. Thus, a system that desires, for example, to decode local programming needs to acquire both a wide area programming network ID and a local programming network ID to decode the local programming, while only the wide area programming network ID is necessary to decode the wide area programming.
The embodiments utilize dedicated OFDM symbols for network IDs. A preferred embodiment is illustrated in
Once network ID information has been encoded into an OFDM structure, it can be transmitted to a wireless device. The wireless device then decodes the symbol structure to determine the network ID(s). Turning to
The acquisition embodiment is utilized to receive the symbol structure 502, 504 in
The network “B” ID symbol is then sampled one or multiple periods. The LB interlaces are descrambled utilizing one of the hypothesis network “B” IDs combined with a network “A” ID in the network “A” candidate set, AM. The network “B” search metric is then calculated and added to the network “B” candidate set, BN, of size N, if it makes it to the top N. This process continues until all the network “A” IDs in the network “A” candidate set are combined with all the network “B” ID hypotheses and tested.
After the network “A” ID/network “B” ID candidate search process finishes, a selection process begins. The selection process is additionally beneficial in terms of time diversity since the search data is from a fraction of one OFDM symbol. Increased time diversity facilitates to make a better selection from a candidate set. The selection metric is calculated for all the candidates from the next network ID symbols. The selection metric, a combination of search metrics from different network ID symbols, therefore, provides more time diversity than the search metric does. The network “A” ID with the best selection metric is selected as the optimum network ID candidate. The network “B” ID is selected from network “A”/network “B” ID combinations that yield the best selection metric score. The design of the selection metric is discussed herein. In one embodiment, the selection process can be avoided by setting M=N=1.
An optimum network “A”/network “B” ID combination is the one with the largest combined search metric:
where S is the number of time diversity combinations from the selection process.
The search metric for the nth TDM pilot network “A”/network “B” symbol is defined as follows for the detected PSD energy, η 916:
is the interference PSD energy 912, sk (i) is the energy 914 of the kth sample under the ith hypothesis and λ is a predetermined constant. The search metric is an unbiased estimate of the total energy of the channel under the hypothesis.
The final search metric with S selection diversity is:
which is the sum of the search metric obtained from both network “A”/network “B” ID symbols to gain time-diversity as well as reduce estimation variance. This search metric does not assume any channel profile and, therefore, is channel profile safe.
In the case of a mismatch between a hypothesis ID and a correct ID, the channel energy of the correct ID broadcast will be evenly spread over the whole 16 bins, and no significant channel energy should be detected in the activity zone utilizing the search metric, i.e., η→0. However, if the hypothesis ID matches the correct ID, the broadcast channel with the correct ID will be dispread, and the channel energy will be confined within the activity zone. For channels who's ID does not match a hypothesis ID, the channel energy will be spread over the whole 16 bins. In this case, significant energy will be detected utilizing the search metric, i.e., η→0.
However, in the case where the pilot samples are not longer than a maximum channel, such as I=1 in
which is always an over-estimate of the interference power spectral density. The search metric defined in (Eq. 2) then becomes:
resulting in a biased estimate (under-estimate) of the energy of the channel under hypothesis. The flatter the channel time response, the greater the bias. In other words, unlike the search metric in (Eq. 2) which is profile independent, the search metric in (Eq. 5) favors the channel with a concentrated profile, although an OFDM receiver in general does not have this discrimination.
In view of the exemplary systems shown and described above, methodologies that may be implemented in accordance with the embodiments will be better appreciated with reference to the flow charts of
Moving on to
If, however, the pilot samples are not longer than the maximum channel 1404, the channel energy is determined by eliminating an average PSD energy from the obtained PSD energy 1416, ending the flow 1414. The average PSD energy is utilized in this instance because no separation between the channel under hypothesis and the interference PSD exists. Utilizing the average PSD energy generally produces an over-estimate of the interference PSD resulting in a biased estimate of the channel under hypothesis.
In one embodiment, a data packet transmitted between two or more communication system components that facilitates data communications is comprised of, at least in part, information relating to a network ID that is communicated with at least one OFDM symbol structure that employs at least one pilot respective of the network ID.
What has been described above includes examples of the embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of the embodiments are possible. Accordingly, the embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.
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|U.S. Classification||370/343, 370/430|
|Cooperative Classification||H04L5/0083, H04L5/0007, H04L27/261, H04L5/0048|
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|Oct 7, 2005||AS||Assignment|
Owner name: QUALCOMM INCORPORATED A DELAWARE CORPORATION, CALI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WANG, MICHAEL MAO;VREELJ, BOJAN;MUKKIAVILLI, KRISHNA KIRAN;AND OTHERS;REEL/FRAME:016859/0473;SIGNING DATES FROM 20050112 TO 20050113
Owner name: QUALCOMM INCORPORATED A DELAWARE CORPORATION, CALI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WANG, MICHAEL MAO;VREELJ, BOJAN;MUKKIAVILLI, KRISHNA KIRAN;AND OTHERS;SIGNING DATES FROM 20050112 TO 20050113;REEL/FRAME:016859/0473
|Jan 30, 2006||AS||Assignment|
Owner name: QUALCOMM INCORPORATED, A CORP. OF DELAWARE, CALIFO
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WANG, MICHAEL MAO;VRCELJ, BOJAN;MUKKAVILLI, KRISHNA KIRAN;AND OTHERS;REEL/FRAME:017218/0541;SIGNING DATES FROM 20050112 TO 20050113
Owner name: QUALCOMM INCORPORATED, A CORP. OF DELAWARE, CALIFO
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WANG, MICHAEL MAO;VRCELJ, BOJAN;MUKKAVILLI, KRISHNA KIRAN;AND OTHERS;SIGNING DATES FROM 20050112 TO 20050113;REEL/FRAME:017218/0541
|May 28, 2014||FPAY||Fee payment|
Year of fee payment: 4